Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.12.016 Byline: Atsushi Takebe (a)(c), Takumi Era (a), Mitsuhiro Okada (a)(b), Lars Martin Jakt (a)(b), Yoshikazu Kuroda (c), Shin-Ichi Nishikawa (a) Keywords: ES cell; In vitro differentiation; DNA microarray; PDGFR[alpha]; ARID3b Abstract: An inherent difficulty in using DNA microarray technology on the early mouse embryo is its relatively small size. In this study, we investigated whether use of ES cell differentiation culture, which has no theoretical limit in the number of cells that can be generated, can improve this situation. Seven distinct ES-cell-derived populations were analyzed by DNA microarray and examined for genes whose distribution patterns are similar to those of PDGFR[alpha], a gene implicated in differentiation of mesoderm/mesenchymal lineages. Using software developed in our laboratory, we formed a group of 30 genes which showed the highest similarity to PDGFR[alpha], 18 of these genes were shown to be involved in development of either mesodermal, mesenchymal or neural crest cells. This list also contains several genes whose role in embryogenesis has not yet been fully identified. One such molecule is mARID3b. The mARID3b expression is found in the paraxial mesoderm and cranial mesenchyme. mARID3b-null mouse showed early embryonic lethality, and most phenotypes of this mutant appear to develop from a failure to generate a sufficient number of cranial mesenchymal cells. These results demonstrate the potential use of ES cell differentiation culture in identifying novel genes playing an indispensable role in embryogenesis. Author Affiliation: (a) Laboratory for Stem Cell Biology, RIKEN Center for Development Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (b) The Foundation for Biomedical Research and Innovation, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (c) Division of Gastroenterological Surgery, Graduate School of Medicine, Kobe University, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan Article History: Received 27 June 2005; Revised 18 November 2005; Accepted 6 December 2005

Identification of novel genes that are similar to platelet-derived growth factor receptor, using DNA microarray studies on mouse embryonic cells, to find their role in embryogenesis is presented.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.12.025 Byline: Siu-Shan Mak (a), Mariko Moriyama (a), Eri Nishioka (b), Masatake Osawa (a), Shin-Ichi Nishikawa (a) Keywords: bcl2; bcl2 null; Melanoblast; c-Kit; Hair follicle development; Melanocyte stem cell; Melanocyte survival; Stem cell development; Stem cell factor Abstract: Bcl2 null mice display a characteristic loss of pigmentation demonstrating the importance of Bcl2 in the melanocyte (Mc) lineage. It was recently reported that this abnormal phenotype is due to the failure of melanocyte stem cell (MSC) maintenance and that Bcl2 is selectively important for the survival of MSCs. However, in our analysis of the same mouse, we observe a reduction in melanoblast (Mb) number in both epidermal and follicular populations. More importantly, there is a complete absence of MSCs. SCF downregulation in the epidermis is concomitant with the dramatic reduction in Mb numbers observed in the Bcl2 null, suggesting that Bcl2 is indispensable for the survival of Mbs in the absence of c-Kit signaling. Consistently, abrogation of c-Kit signaling in Bcl2 null mice depletes all Mbs and Mcs, whereas continuous expression of SCF in epidermal keratinocytes rescues the MSCs. Our results demonstrate that Bcl2 has a general role in Mb and Mc survival and is essential for the emergence of MSCs. Moreover, the results indicate that the first wave of Mcs that provide hair pigmentation is derived directly from epidermal Mbs bypassing MSCs. Furthermore, a Bcl2-independent mechanism of action of SCF in the Mc lineage is revealed as SCF c-Kit signaling is functional in the absence of Bcl2. Author Affiliation: (a) RIKEN, Center for Developmental Biology (CDB), Laboratory for Stem Cell Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (b) Division of Dermatology, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan Article History: Received 29 July 2005; Revised 6 December 2005; Accepted 9 December 2005

The Foxl1 gene, which encodes a winged helix transcriptional regulator, is expressed in the mesenchymal layer of developing and mature gastrointestinal tract. Foxl1-deficient mice exhibit various defects not only in the epithelial layer of the gastrointestinal tract but also in gut-associated lymphoid tissues. In the small intestine of Foxl1-deficient mice, the formation of Peyer's patches is affected, particularly in the caudal region. This alteration is shown to be due to the delayed formation of Peyer's patches organizing centers as revealed by the expressions of VCAM1 and IL-7 receptor [alpha]-chain at 17.5 days postcoitus. Peyer's patch defects are concordant with the significantly decreased expression of Lymphotoxin [beta]-receptor in the caudal region of fetal intestine. Foxl1 is suggested to regulate the responsiveness of fetal intestinal mesenchymal cells to inductive signals mediated by Lymphotoxins during Peyer's patch organogenesis. In addition, constitutive outgrowth of colonic patches due to defects in radioresistant stromal components of colonic patches are seen in Foxl1-deficient mice. Because of the functional similarities of hypertrophic colonic patches to those seen in hapten-induced experimental colitis, this hypertrophy is suggested to involve Lymphotoxin [beta]-receptor signaling. Together, the data suggest that Foxl1 might be involved in cellular responses of gut-associated lymphoid tissues dependent upon the Lymphotoxins/Lymphotoxin [beta]-receptor axis. Keywords: Foxl1; Peyer's patch; Colonic patch; Gut mesenchyme; Lymphotoxins; Mouse

Melanocytes (Mc) and their progenitors melanoblasts (Mb) are derived from the neural crest and migrate along the dorsolateral pathway to colonize the dermis, the epidermis, and finally the hair matrix. To examine the involvement of cadherins in the migration of Mc lineage cells, we combined flow cytometric analysis of dissociated live cells with immunohistochemical staining of tissue sections to quantify the level of cadherin expression on the surface of Mb/Mc. At 11.5 days postcoitum, Mb are in the dermis and are E-cadherin(super -)P-cadherin(super -) (E-cad(super -)P-cad(super -)). During the next 48 h, a 200-fold increase of E-cadherin expression is induced on the surface of Mb prior to their entry into the epidermis, thereby forming a homogeneous E-cad(super high)p-cad(super -/low) population. The cadherin expression pattern then diversifies, giving rise to three populations, an E-cad(super -)P-cad(super -) dermal population, E-cad(super high)P-cad(super low) epidermal population, and E-cad(super -)P-cad(super med.high) follicular population. In all three populations, the patterns of expression are region-specific, being identical with those of surrounding cells such as keratinocytes and fibroblasts, and are preserved before and after pigmentation. While most of the epidermal Mb/Mc disappear after the neonatal stage in normal mice, forced expression of steel factor in the epidermis of transgenic mice promotes survival of epidermal Mb/Mc, maintaining epidermal-type cadherin expression pattern (E-cad(super high)P-cad(super low)) throughout the postnatal life. These findings indicate the involvement of extrinsic cues in coordinating the cadherin expression pattern of Mb/Mc and suggest a role for E- and P-cadherins in guiding Mc progenitors to their final destinations. Key Words: melanocyte; melanoblast; cadherins; E-cadherin; P-cadherin; expression; migration; diversification; colonization; quantitative; qualitative; microenvironment; steel factor (SLF); flow cytometry; epidermis; dermis; hair follicles; hair matrix.

Ovarian follicle development is controlled by the cycling variation of gonadotrophins derived from the central nervous system. Intragonadal signals are also required, especially in the autonomous development of small follicles. Receptor tyrosine kinase c-kit and its ligand SLF (Steel factor) are expressed on the surface of specific populations of follicle-forming cells in a contiguous manner and are thought to have important roles in follicular development. We blocked the interaction of c-kit and its ligand by administering the function-blocking antibody ACK2 to developing mice at various times after birth and monitored ovarian follicle development. A blockade of c-kit function disturbed the onset of primordial follicle development, primary follicle growth, follicular fluid formation of preantral follicles, and Penultimate-stage ovarian follicle maturation before ovulation. Ovarian follicle growth was dependent on c-kit during the first 5 days after birth when the functional FSH receptor is not yet expressed in mouse ovary. In contrast, primordial follicle formation and survival, small preantral or antral follicle development, ovulation, and luteinization of the ovulated follicle were not affected by this antibody. These findings indicate the stepwise requirement of c-kit and its ligand interaction system in the developing ovarian follicle and that c-kit with its ligand supports the autonomous development of ovarian follicle independent of gonadotrophins.